PhD Defence - Bryn Knight

PhD Candidate

Bryn Knight

Abstract

Degeneracy corrections to neutron capture rates in neutron-dense

Heavy element synthesis within stellar bodies typically manifests in explosive environments such as neutron star mergers. These potential sites present high enough neutron densities that facilitate neutron degeneracy. In this work, we study the effect of neutron degeneracy on stellar capture rates for nuclei ranging from stability to the neutron drip line. We investigate how degeneracy can alter traditional reaction rates over a range of thermodynamic conditions that are typical of the r-process, and within the crust of accreting neutron stars. We have provided an analytical approximation as well as tabulated data of our degenerate rates for wide use in the nuclear astrophysics community. Our results show that degeneracy can change the capture of neutrons by orders of magnitude compared to captures under strictly explosive conditions. As well, we demonstrate how thermally populated targets can alter the capture of degenerate neutrons. Our corrections to stellar neutron capture rates may lead to changes in the abundance evolution of r-process elements. Furthermore, they may help interpret the abundance evolution of rp-process ashes, and the accreting crust's cooling following X-ray bursts.

Examination Committee

• Dr. Eric Poisson, Chair
• Dr. Liliana Caballero, Advisor
• Dr. Rachid Ouyed, Advisory Committee
• Dr. Michael Massa, Graduate Faculty
• Dr. Fernando Montes, External Examiner (Michigan State University)